CVE-2025-68774 | In the Linux kernel, the following vulnerability has been resolved: hfsplus: fix missing hfs_bnode_get() in __hfs_bnode_create When sync() and link() are called concurrently, both threads may enter hfs_bnode_find() without finding the node in the hash table and proceed to create it. Thread A: hfsplus_write_inode() -> hfsplus_write_system_inode() -> hfs_btree_write() -> hfs_bnode_find(tree, 0) -> __hfs_bnode_create(tree, 0) Th
In the Linux kernel, the following vulnerability has been resolved:
hfsplus: fix missing hfs_bnode_get() in __hfs_bnode_create
When sync() and link() are called concurrently, both threads may
enter hfs_bnode_find() without finding the node in the hash table
and proceed to create it.
Thread A:
hfsplus_write_inode()
-> hfsplus_write_system_inode()
-> hfs_btree_write()
-> hfs_bnode_find(tree, 0)
-> __hfs_bnode_create(tree, 0)
Thread B:
hfsplus_create_cat()
-> hfs_brec_insert()
-> hfs_bnode_split()
-> hfs_bmap_alloc()
-> hfs_bnode_find(tree, 0)
-> __hfs_bnode_create(tree, 0)
In this case, thread A creates the bnode, sets refcnt=1, and hashes it.
Thread B also tries to create the same bnode, notices it has already
been inserted, drops its own instance, and uses the hashed one without
getting the node.
```
node2 = hfs_bnode_findhash(tree, cnid);
if (!node2) { next_hash = tree->node_hash[hash];
tree->node_hash[hash] = node;
tree->node_hash_cnt++;
} else { hash_lock);
kfree(node);
wait_event(node2->lock_wq,
!test_bit(HFS_BNODE_NEW, &node2->flags));
return node2;
}
```
However, hfs_bnode_find() requires each call to take a reference.
Here both threads end up setting refcnt=1. When they later put the node,
this triggers:
BUG_ON(!atomic_read(&node->refcnt))
In this scenario, Thread B in fact finds the node in the hash table
rather than creating a new one, and thus must take a reference.
Fix this by calling hfs_bnode_get() when reusing a bnode newly created by
another thread to ensure the refcount is updated correctly.
A similar bug was fixed in HFS long ago in commit
a9dc087fd3c4 ("fix missing hfs_bnode_get() in __hfs_bnode_create")
but the same issue remained in HFS+ until now.
- 🔗 git.kernel.org/stable/c/3b0fc7af50b896d0f3d104e70787ba19…
- 🔗 git.kernel.org/stable/c/39e149d58ef4d7883cbf87448d39d512…
- 🔗 git.kernel.org/stable/c/b68dc4134b18a3922cd33439ec614aad…
- 🔗 git.kernel.org/stable/c/b9d1c6bb5f19460074ce9862cb80be86…
- 🔗 git.kernel.org/stable/c/457f795e7abd7770de10216d7f9994a3…
- 🔗 git.kernel.org/stable/c/5882e7c8cdbb5e254a69628b780acff8…
- 🔗 git.kernel.org/stable/c/152af114287851583cf7e0abc1012994…
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CVE-2025-68774 | In the Linux kernel, the following vulnerability has been resolved: hfsplus: fix missing hfs_bnode_get() in __hfs_bnode_create When sync() and link() are called concurrently, both threads may enter hfs_bnode_find() without finding the node in the hash table and proceed to create it. Thread A: hfsplus_write_inode() -> hfsplus_write_system_inode() -> hfs_btree_write() -> hfs_bnode_find(tree, 0) -> __hfs_bnode_create(tree, 0) Th
In the Linux kernel, the following vulnerability has been resolved: hfsplus: fix missing hfs_bnode_get() in __hfs_bnode_create When sync() and link() are called concurrently, both threads may enter hfs_bnode_find() without finding the nod